Process of refining hydrocarbons



Patented May 8, 1934 PROCESS OF REFINING HYDROCARBONS Robert I. Lewis,Wilmington, Calif., assignor to Shell Development Company, SanFrancisco, Calif., a corporation of Delaware No Drawing. ApplicationJuly 15, 1929, Serial No. 378,572

Claims.

My invention relates to a process for the refining of hydrocarbons,especially petroleum, and refers especially to a process for treatingpetroleum oils for the manufacture of gasoline or mo- 1 tor fuels.

The sulphur content of those petroleum oils utilized as motor fuels isspecified, in this country, as not being over 0.1 of 1%. Since the motorfuels secured as a result of both straight run and cracking processesnormally contain sulphur in excess of this value, they must be treatedto reduce the sulphur content.

The treating processes usually involve the contacting of the oil with areagent whereby a portion of the bodies containing the sulphur areremoved. Usually a sludge is formed when the reagent and oil arecontacted. This sludge contains the sulphur bodies removed from the oiltogether with a portion of the oil with which the reagent has reacted toform heavier constituents. It is of course readily apparent that theideal treatment, from the standpoint of economy, would be the one inwhich only the sulphur bodies are removed, the oil being otherwiseunchanged. The desirability of such a process is further enhanced by thefact that those portions of the oil with which the reagent reacts are,in many instances, those which assure the best performance and highestefiiciency of the engine in which they are utilized.

Various processes have recently been proposed for the treatment ofpetroleum wherein the treating loss is said to be materially reduced. Inone of these it has been proposed to treat with sulphuric acid at atemperature below 38 F. I have found that such a cold treatment has amarked disadvantage, as is set forth in the copending application Ser.No. 308,583, filed September 26, 1928, in that upon the distillation ofthe treated distillate a portion of the sulphur compounds distills overwith the gasoline. This, as is readily apparent, is extremelyundesirable for it obviates entirely the effect of a goodly portion ofthe treatment to remove the sulphur bodies.

It is therefore an object of my invention to provide a process forremoving the sulphur bodies from a hydrocarbon oil which can be carriedout in such a manner that the hydrocarbon oil produced contains thedesired minimum sulphur content.

A further object of my invention is to provide a process by which agasoline or motor fuel may be produced having the desired qualitycharacteristics.

55 Further objects of my invention will appear in the followingspecification in which I have set forth the preferred process of myinvention. It is to be understood that the invention, as defined by theappended claims, is to be accorded a range of equivalents consistentwith the state of the prior art.

My invention may be briefly characterized as comprising the treatment ofa hydrocarbon with a relatively weak reagent at a normal or roomtemperature and of about F., treating the hydrocarbon with a relativelystrong reagent at a substantially lower temperature, and furthertreating the hydrocarbon with a relatively strong reagent at a normaltemperature.

In the following I will describe the invention in connection withpressure distillate, the name usually applied to the gasoline fractionsecured as a result of the cracking of a heavier oil. However, it is tobe understood, that my invention is applicable to other hydrocarbons andother petroleum fractions. Further I will describe my invention inconnection with the use of sulphuric acid as the treating reagent. Othermaterials as well as sulphuric acid may be used for the treating ofhydrocarbon oils and, accordingly, I do not wish to limit my inventionto the use of only sulphuric acid since such other materials ashydrochloric acid and nitric acid can be utilized.

One process which I have preferably utilized in treating pressuredistillate was conducted in the following mannerz-To the pressuredistillate at normal atmospheric temperature 27 B. sulphuric acid(containing 31% H2SO4) amount to 5% by volume of the pressure distillate(25.8 pounds per barrel) was added in one dump. The mixture was agitatedfor about 30 minutes after which it was allowed to settle. The spentacid was drained off and the distillate chilled to about 20 F. One dumpof four pounds per barrel of 100% I-I2S04 as 97.4% acid was then added.With the temperature maintained substantially between 15 and 20 F. themixture was agitated and allowed to settle. The sludge was drained offand another dump of 5 pounds per barrel of the same acid was added. Withthe low temperature similarly maintained the mixture was agitated,settled and drained. Subsequently the distillate was brought up tonormal atmospheric temperature and four pounds per barrel of 100% H2804as 97.4% acid was added in two equal dumps. After agitation, settlingand removal of the sludge the distillate was subjected to the regularneutralization. It was then distilled with Ell " continuous manner.

' mal temperature.

steam and fractionated and the gasoline recovered in the usual manner.

The original pressure distillate contained. 0.8 of 1% of sulphur and thedoctor and other quality tests indicated that a high percentage of veryobjectionable sulphur bodies were present. After treatment according tothe above process, the sulphur content had been reduced below therequired minimum and the quality tests were all highly satisfactory.Samples of the distillate were subjected to sunlight continuously for aweek at the end of which time the Saybolt color had only dropped from to26. During this period there was no indication of gum formation. Thisindicates a high degree of stability under very severe test conditions.

The same pressure distillate, when treated in the manner practicedbefore the process of my invention was known, did not result in agasoline having as low a sulphur content, did not give as excellentresults in the sulphur corrosion tests, nor the highly desirable colorstability.

By the employment of apparatus well known in the art the process isreadily conducted in a It is of course to be understood that thesulphuric acid employed during the cold treat must be one whose freezingpoint is not above the temperature employed. If this precaution is notobserved the freezing of lines,

pump and agitators may occur if the temperature is carried too low.

The acid added to the chilled distillate has, I believe, a solventaction upon part of the sulphur compounds to a greater extent than acidof nor- The remaining sulphur compounds do not undergo, apparently, araise in boiling point probably because of less polymerization.Consequently, upon redistillation these do not remain in the stillbottoms but vaporize and come over with the gasoline. The subsequenttreatment of the cold treated distillate with acid at normal temperaturefinishes the treating of the distillate, apparently by polymerization ofthe sulphur bodies which have not been removed by the cold treatment, insuch a manner that they do not distill over subsequently with thedistillate.

I have also found it desirable in treating distillates to add the sameamount of reagent, in certain instances, in smaller quantities for eachoperation than I have here set forth, thus making for a greater numberof treating operations. This generally results in a reduced sulphurcontent of the distillate for the same amount of reagent. I am now orthe opinion that this is w due to the fact that when the reagent isadded in one large dump a portion of it is utilized to polymerize theundissolved sulphur bodies which uses up the reagent. When the reagentis added in smaller amounts a greater relative percentage is effectivein dissolving the sulphur bodies while only a small portion is lost inthe polymerizing or" the remaining bodies.

While the processes herein described are well adapted to accomplish thepurposes of this invention, it is to be appreciated that variousmodifications may be made Without departing from the spirit of theinvention. Thus, depending upon the hydrocarbon being treated, it may bedesirable to utilize sulphuric acid of different strengths from thatwhich I have set forth in the sample given. The temperatures and theorder of the steps outlined may also be varied to secure a moreeflicient treatment. Hydrocarbon mixtures, such as petroleum, vary so incharacter that the most eihcient manner of treatment for each cannot bespecified but must be determined by a certain amount of experimentation.

I claim:

1. The process of treating a hydrocarbon oil which comprises contactingthe oil with sulphuric acid of relatively low concentration at a normaltemperature of about ER, separating the spent acid from the oil,chilling the oil to at least 38 contacting the chilled oil withconcentrated sulphuric acid whereby additional sludge is formed,separating the additional sludge from the oil, raising the temperatureof the oil, contacting the oil with concentrated sulphuric acid at anormal temperature of about 70 F. whereby a further sludge is formed,and separating the further sludge from the oil.

2. The process of treating a hydrocarbon oil which comprises contactingthe oil with sulphuric acid of relatively low concentration at a normaltemperature of about 70 separating the spent acid from the oil, chillingthe oil to at least 38 F., contacting the chilled oil with concentratedsulphuric acid whereby additional sludge is formed while maintaining theoil chilled, separating the additional oil sludge from the oil, raisingthe temperature of the oil, contacting the oil with concentratedsulphuric acid at a normal temperature of about 70 F. whereby a furthersludge is formed, and separating the further sludge from the oil.

3. The process of treating a hydrocarbon oil substantially as set forthin claim 1, but in which the volume of sulfuric acid of at least oneconcentration used in the process is divided into a number of fractionsfor treating oil in the corresponding number of successive operations.

i. The process of treating a hydrocarbon oil which comprises treatingthe oil with sulphuric acid of a relatively low concentration and at anormal atmospheric temperature of about 70 F., separating spent acidfrom the oil, then chilling said oil substantially to a temperaturelower than 38 F., treating said chilled oil with separate volumes of aconcentrated sulphuric acid in a series of at least two steps wherebysludge. is formed, and separating sludge from the oil after each step,then raising the temperature of the oil, treating said oil withconcentrated sulphuric acid at a normal atmospheric temperature of about70 F. whereby further sludge is formed, and separating said furthersludge from said oil.

5. In the process of treating a hydrocarbon oil the steps which comprisetreating the oil with sul-.- furic acid of about 27 B. at a normaltemperature of about 70 F., separating the treated oil 135 from thespent acid, chilling the oil to about 20 F., treating the chilled oilwith sulfuric acid of about 100% concentration whereby sludge is formed,separating the oil from the sludge, raising the temperature of the oil,treating the oil with 140 concentrated sulfuric acid at a normaltemperature of about 70 F. whereby a further sludge is formed, andseparating this sludge from the oil.

ROBERT I. LEWIS.

